Electromagnetically actuated pilot valves are used in high pressure hydraulics, in particular in mining and, more specifically, in electro-hydraulic support control systems. They are used for switching subsidiary main valves by means of which apparatus, for example, hydraulic rams and props are actuated. The pilot valves designed as multi-path valves are switched with low switching forces and extremely small switching paths owing to the leverage of the associated switch levers.
The known pilot valves, may be embodied in devices of the type described, for example, in GB-A-2226110 and DE-PS 36 20 242. Such devices have, in the housing bores of a cuboid housing, valve inserts which contain the functional parts of the valves such as, in particular, the closure elements e.g., valve balls, valve seating members, coupling rods and valve springs together with guide parts receiving these other parts. The valves are usually actuated by electro-magnetic force exerted on levers which pivot through a small path of movement. For adjusting the switching action, the levers are often provided with adjusting screws against which a tappet or ram acting on the valve closure elements and guided in the valve insert rests.
Known valve devices employ valve inserts with a relatively large number of functional parts and they therefore demand relatively high production costs and also have relatively large dimensions. The reliability of operation is not always dependably ensured under the conditions of underground mining. Adjustment of the switching path by means of the adjusting screws arranged on the switch levers is frequently insufficiently precise for exact adjustment of the pilot valves. In particular, exact valve seating adjustments cannot be achieved. It should be taken into consideration that, with the necessary extremely small dimensions of the pilot valves and the extremely small switch paths which are about 0.1 mm or much lower owing to the leverage, accurate valve seating adjustment may only be achieved with difficulty.
An object of the invention is to provide an improved valve device with which sensitive valve seating adjustment may be achieved with the possibility of after-adjustment, wherein a simplified overall design of the device and a compact construction thereof are to be achieved if at all possible.